Recently, researches for mounting, on automobiles, (hereinafter, referred to as vehicles) an automatic driving system which travels on a preset or estimated traveling route while avoiding collision with other moving bodies and obstacles in the vicinity of the automobiles or a driving support system which supports driver's driving operation have been promoted.
Such automatic driving system and driving support system use an external recognition sensor mounted on a vehicle to recognize moving bodies and obstacles such as other vehicles existing in the vicinity of a host vehicle, lane marks which partition lanes on a road on which a host vehicle travels, a road mark, and the like, and performs automatic driving and driving support of the host vehicle based on these surrounding environment information.
As a function example of the automatic driving or driving support, there is a lane change function of changing from a traveling lane on which the host vehicle is traveling to any one of left and right adjacent lanes. For example, in the lane change function in the automatic driving system, the lane to be driven is automatically changed based on a lane change request from a driver or a lane change request determined on the automatic driving system.
In addition, in the lane change function in the driving support system, when a driver performs the lane change operation, there is a function of determining that safety such as whether there is a possibility that the host vehicle collides with the surrounding moving bodies due to the lane change can be secured and providing the determination information to the driver.
In such lane change function, target marker information (traveling direction line) to be followed up by a vehicle is generated based on lane marker information (also referred to as lane mark information and lane marker information) which defines (partitions) the lanes. Therefore, it is important to obtain not only lane marker information of a lane on which a vehicle is currently traveling (hereinafter, referred to as a lane before change of lane) but also lane marker information of a lane on which a vehicle is traveling after a lane is changed (hereinafter, referred to as a lane after change of lane). Here, a white line (lane mark) or the like drawn on a road is known for partitioning a lane, and the lane marker information is generated by recognizing this white line by the external recognition sensor.
However, with only a front camera photographing a front of a vehicle, the lane marker located on a far side of a lane after change of lane (definition will be described later) as viewed from the lane before change of lane is not in a visual field of the front camera sufficiently, such that it is difficult to obtain the accurate lane marker information. In addition, when another vehicle is traveling on the lane after change of lane, the lane marker may be shielded by the other vehicle. As a result, it becomes difficult to obtain the lane marker information on the far side of the lane after change of lane.
Here, the far side or the near side of the lane marker means the following. The lane after change of lane adjacent to the lane before change of lane on which a vehicle is currently traveling is formed by a lane marker which is common to the lane before change of lane and the lane after change of lane and by an outside lane marker which is paired with this common lane marker and partitions the lane after change of lane. Therefore, when viewed from the host vehicle, the lane marker which is common to the lane before change of lane and the lane after change of lane becomes a lane marker on near side and the outside lane marker which forms the lane after change of lane becomes a lane marker on far side. For example, if the traveling vehicle changes to a right lane, a left lane marker of the lane after change of lane becomes a lane marker on near side and a right lane marker of the lane after change of lane becomes a lane marker on far side.
In order to solve such problem, JP 11-167636 A (PTL 1) discloses a method for mounting a side camera for photographing the side of the vehicle to estimate a position of a lane marker of a lane on which a host vehicle travels. In PTL 1, the front camera photographing the front of the vehicle and the side camera photographing the side just under the vehicle are mounted, and the lane marker information by the front camera and the lane marker information by the side camera are combined, thereby estimating the lane marker information of the lane on which the host vehicle is traveling.